Cerrig Sion Crydd Out to sea to the west of the mouth of the River Dwyfor there is a row of thirteen rocks called “Sion Crydd’s Rocks”. These can only be seen at very low tides or when the sea is calm and the water is clear. Sion was a cobbler from Llanystumdwy who sometimes referred to them as his cows so some called them “Sion Crydd’s Cattle”. During the Second War, and for many years afterwards, there was a target positioned on it that was used by aeroplanes from the bombing school at Penrhos and the Royal Navy gunnery training school at Penychain. It was a good place to catch mackerel.